Each phase of a multi-phase voltage converter includes a power stage, passive circuit, synchronous rectification (SR) switch, and control circuit. Each passive circuit couples its power stage to an output node of the voltage converter, and is switchably coupled to ground by the SR switch. The current through the SR switch has a half-cycle sinusoidal shape with a resonant frequency determined by the reactance of the passive circuit. The control circuit generates signals to control switches within the power stage and the SR switches. The control circuit measures current through the SR switch of each phase, and adjusts the duty cycles of the control signals for the phases so that the SR switches are switched off when zero or almost zero current is flowing through them.
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1. A multi-phase voltage converter, comprising: a plurality of phases, each phase comprising a synchronous rectification (SR) switch through which a half-cycle sinusoidal-like current is conducted when turned on; and a control circuit operable to: control cycle-by-cycle switching of each phase via respective pulse width modulation (PWM) control signals, each PWM control signal having a switching period and duty cycle; select one of the phases as a reference phase, wherein the switching period and duty cycle of the PWM control signal for the reference phase are set such that the half-cycle sinusoidal-like current conducted by the SR switch of the reference phase crosses zero or nearly crosses zero when the SR switch is turned off each switching cycle; set the switching period and duty cycle of the PWM control signals for the other phases to that of the reference phase; and adjust the duty cycle of the PWM control signals for the other phases such that the half-cycle sinusoidal-like current conducted by the SR switches of the other phases eventually cross zero or nearly cross zero when the SR switches are turned off each switching cycle.
A multi-phase voltage converter has multiple phases, each with a synchronous rectification (SR) switch carrying a sinusoidal-like current when on. A control circuit adjusts each phase's switching using pulse width modulation (PWM) signals, which have a switching period and duty cycle. One phase is the "reference." Its PWM settings are tuned so its SR switch current crosses zero (or nearly zero) when it turns off. The other phases initially copy the reference phase's PWM settings. Then, the control circuit tweaks each of their duty cycles so their SR switch currents also cross zero (or nearly zero) when their SR switches turn off. This ensures efficient switching by minimizing current flow during turn-off.
2. The multi-phase voltage converter of claim 1 , wherein each of the phases further comprises: a high-side switch connected between an input voltage terminal and a switching node; a low-side switch connected between the switching node and ground; and a passive circuit connecting the switching node to a common output node of the multi-phase voltage converter, wherein the SR switch of the phase is connected between the passive circuit and ground.
Each phase of the multi-phase voltage converter described in the previous claim includes a high-side switch connecting to an input voltage, a low-side switch connecting to ground, and a passive circuit linking a switching node to a common output node. The SR switch is connected between the passive circuit and ground. This topology facilitates synchronous rectification, where the SR switch minimizes power loss by conducting current only when the voltage polarity is favorable, achieving higher efficiency compared to using a diode. The passive circuit helps shape the current waveform to achieve the desired sinusoidal-like current for zero-current switching.
3. The multi-phase voltage converter of claim 1 , wherein the control circuit is operable to: decrease the duty cycle of the PWM control signal for each of the other phases which is faster than the reference phase; and increase the duty cycle of the PWM control signal for each of the other phases which is slower than the reference phase.
A multi-phase voltage converter includes a control circuit that adjusts the duty cycle of pulse-width modulation (PWM) control signals for multiple phases to synchronize their switching frequencies. The converter operates in a multi-phase configuration where each phase generates an output voltage through switching elements controlled by PWM signals. The control circuit monitors the switching frequencies of each phase and compares them to a reference phase. For phases that switch faster than the reference, the control circuit decreases the duty cycle of their PWM signals to slow them down. Conversely, for phases that switch slower than the reference, the control circuit increases the duty cycle of their PWM signals to speed them up. This adjustment ensures that all phases operate at the same switching frequency, improving efficiency and reducing ripple in the output voltage. The control circuit dynamically adjusts the duty cycles based on real-time frequency comparisons, maintaining synchronization across all phases. This method enhances the performance of multi-phase voltage converters by balancing the switching frequencies and minimizing phase discrepancies.
4. The multi-phase voltage converter of claim 3 , wherein the control circuit is operable to compare current measurements for the reference phase to current measurements for the other phases to determine whether each of the other phases is faster or slower than the reference phase.
To determine whether a non-reference phase is "faster" or "slower" than the reference phase, the control circuit of the multi-phase voltage converter (as previously described) compares current measurements. It monitors the SR switch current in each phase and compares it to the reference phase's SR switch current. By analyzing these current measurements, the control circuit can determine if a particular phase is leading or lagging the reference phase, and adjust the duty cycle accordingly to achieve optimal phase alignment and zero-current switching for improved efficiency.
5. The multi-phase voltage converter of claim 4 , wherein the control circuit is operable to identify an individual one of the other phases as being faster than the reference phase if the current measurements for that other phase decrease to zero in less time than the current measurements for the reference phase, and wherein the control circuit is operable to identify an individual one of the other phases as being slower than the reference phase if the current measurements for that other phase decrease to zero in more time than the current measurements for the reference phase.
In the described multi-phase voltage converter, the control circuit determines if a non-reference phase is "faster" by observing if its SR switch current drops to zero in *less* time than the reference phase's SR switch current. Conversely, it identifies a phase as "slower" if its SR switch current takes *more* time to reach zero compared to the reference phase. This comparison allows the controller to dynamically adjust the PWM duty cycle of each phase ensuring zero-current switching which maximizes efficiency. This avoids hard switching and reduces power loss.
6. The multi-phase voltage converter of claim 4 , wherein the control circuit is operable to adaptively adjust the duty cycle of the PWM control signals for the other phases such that the current measurements for the other phases eventually cross zero or nearly cross zero when the PWM control signals for the other phases transition from an active state to an inactive state each switching cycle.
The control circuit in the multi-phase voltage converter adaptively adjusts the PWM duty cycles of the non-reference phases. The goal is for the SR switch current in these phases to reach (or nearly reach) zero at the exact moment the PWM control signal switches from active to inactive (turning the SR switch off). This adaptive adjustment mechanism continuously monitors the current and adjusts the duty cycle to ensure optimal zero-current switching which reduces stress and loss. The adjustments are performed dynamically during each switching cycle.
7. The multi-phase voltage converter of claim 1 , wherein the control circuit is operable to align the other phases during the present switching cycle based on the switching period of the reference phase for the immediately preceding switching cycle.
The control circuit in the described multi-phase voltage converter aligns the phases in the *current* switching cycle by referencing the switching period of the *previous* cycle of the designated reference phase. This means the control circuit uses the timing data from the immediately preceding cycle of the reference to synchronize the other phases for the present cycle. This approach provides a stable and responsive method for maintaining phase alignment and enabling zero-current switching for higher converter efficiency.
8. The multi-phase voltage converter of claim 7 , wherein the control circuit is operable to adjust the switching period of the other phases responsive to a transient condition at a load coupled to the multi-phase voltage converter so that the phases remain aligned during the transient condition.
In the described multi-phase voltage converter, when a transient event occurs on the load connected to the converter, the control circuit adjusts the switching period of the non-reference phases to maintain phase alignment. This adjustment compensates for changes in load conditions, ensuring the SR switch currents still reach zero (or nearly zero) during turn-off, even during sudden load changes. This maintains efficient operation by minimizing losses during transient events. The adjustment is performed in real-time in response to the load.
9. The multi-phase voltage converter of claim 8 , wherein the control circuit is operable to increase the switching period of the other phases by a first predetermined amount responsive to a step-up transient condition at the load so that the phases remain aligned during the step-up transient condition.
When a "step-up" transient (sudden increase in load) occurs in the multi-phase voltage converter, the control circuit *increases* the switching period of the non-reference phases by a specific amount. This increase ensures the phases remain aligned despite the load change, maintaining zero-current switching and optimal converter performance during this condition. The amount of adjustment is pre-determined, and allows the converter to quickly adapt to the changing load.
10. The multi-phase voltage converter of claim 8 , wherein the control circuit is operable to decrease the switching period of the other phases by a second predetermined amount responsive to a step-down transient condition at the load so that the phases remain aligned during the step-down transient condition.
Conversely, when a "step-down" transient (sudden decrease in load) occurs in the multi-phase voltage converter, the control circuit *decreases* the switching period of the non-reference phases by a second pre-determined amount. This decrease ensures the phases remain aligned during the step-down transient, maintaining zero-current switching and optimal converter performance. The controller reacts dynamically to the transient condition to maintain synchronous rectification.
11. The multi-phase voltage converter of claim 1 , wherein for each phase, the passive circuit comprises an LC tank coupled to the switching node of that phase and a transformer/tapped inductor for coupling the LC tank to an output capacitor of the multi-phase voltage converter, and the SR switch is coupled between the transformer/tapped-inductor and ground.
In each phase of the multi-phase voltage converter, the passive circuit consists of an LC tank (inductor and capacitor) connected to the phase's switching node. A transformer or tapped inductor couples the LC tank to the output capacitor of the overall converter. The SR switch is connected between the transformer/tapped inductor and ground. The LC tank and transformer work together to resonate and shape the current waveform to enable the zero-current switching operation, minimizing losses and improving efficiency.
12. A method of phase alignment for a multi-phase voltage converter, each phase of the multi-phase voltage converter including a synchronous rectification (SR) switch through which a half-cycle sinusoidal-like current is conducted when turned on, the method comprising: controlling cycle-by-cycle switching of each phase via respective pulse width modulation (PWM) control signals, each PWM control signal having a switching period and duty cycle; selecting one of the phases as a reference phase, wherein the switching period and duty cycle of the PWM control signal for the reference phase are set such that the half-cycle sinusoidal-like current conducted by the SR switch of the reference phase crosses zero or nearly crosses zero when the SR switch is turned off each switching cycle; setting the switching period and duty cycle of the PWM control signals for the other phases to that of the reference phase; and adjusting the duty cycle of the PWM control signals for the other phases such that the half-cycle sinusoidal-like current conducted by the SR switches of the other phases eventually cross zero or nearly cross zero when the SR switches are turned off each switching cycle.
A method for aligning phases in a multi-phase voltage converter involves controlling the switching of each phase using PWM signals with a switching period and duty cycle. Each phase has a SR switch that conducts a sinusoidal-like current. First, select a reference phase and set its PWM settings so its SR switch current crosses zero (or nearly zero) when it turns off. Then, copy those PWM settings to the other phases. Finally, adjust the duty cycle of the PWM signals for these other phases so their SR switch currents also cross zero (or nearly zero) when their SR switches turn off. This ensures efficient operation by minimizing current during turn-off.
13. The method of claim 12 , wherein adjusting the duty cycle of the PWM control signals for the other phases comprises: decreasing the duty cycle of the PWM control signal for each of the other phases which is faster than the reference phase; and increasing the duty cycle of the PWM control signal for each of the other phases which is slower than the reference phase.
In the method of phase alignment for multi-phase voltage converters, the duty cycle adjustment involves decreasing the duty cycle for phases that are "faster" than the reference phase (current reaches zero early) and increasing the duty cycle for phases that are "slower" than the reference phase (current reaches zero late). This feedback mechanism continually adjusts the timing of the phases to match the reference and maintain zero-current switching, improving the overall efficiency of the converter. The adjustment ensures proper synchronous rectification.
14. The method of claim 13 , further comprising: comparing current measurements for the reference phase to current measurements for the other phases to determine whether each of the other phases is faster or slower than the reference phase.
The method of phase alignment for multi-phase voltage converters further includes comparing current measurements from each phase to the reference phase to determine if each phase is running "faster" or "slower". By monitoring the current in the SR switches and comparing their timing to the reference phase, the system can determine the direction and magnitude of the required duty cycle adjustment to achieve optimal phase alignment and zero-current switching for efficient converter operation.
15. The method of claim 14 , wherein determining whether each of the other phases is faster or slower than the reference phase comprises: identifying an individual one of the other phases as being faster than the reference phase if the current measurements for that other phase decrease to zero in less time than the current measurements for the reference phase; and identifying an individual one of the other phases as being slower than the reference phase if the current measurements for that other phase decrease to zero in more time than the current measurements for the reference phase.
The method for determining if a phase is "faster" or "slower" than the reference phase involves measuring how long it takes the SR switch current to reach zero. If the current reaches zero in *less* time than the reference phase, it's considered "faster." If the current takes *more* time to reach zero, it's considered "slower." These measurements are used to adjust the duty cycle to achieve optimal phase alignment and zero-current switching. This reduces switching losses in the converter.
16. The method of claim 14 , wherein adjusting the duty cycle of the PWM control signals for the other phases comprises: adaptively adjusting the duty cycle of the PWM control signals for the other phases such that the current measurements for the other phases eventually cross zero or nearly cross zero when the PWM control signals for the other phases transition from an active state to an inactive state each switching cycle.
The method of phase alignment for multi-phase voltage converters includes adaptively adjusting the PWM duty cycles of the non-reference phases to ensure the SR switch current reaches (or nearly reaches) zero precisely when the PWM signal turns off the switch. This continuous adjustment allows the system to dynamically compensate for variations in component characteristics, temperature, and operating conditions, ensuring sustained zero-current switching and maximizing converter efficiency. This is done on a cycle-by-cycle basis.
17. The method of claim 12 , further comprising: aligning the other phases during the present switching cycle based on the switching period of the reference phase for the immediately preceding switching cycle.
The method of phase alignment for multi-phase voltage converters aligns the phases in the current switching cycle by using the switching period of the reference phase from the *previous* switching cycle. This approach provides a stable and responsive mechanism for synchronizing the phases and ensuring zero-current switching, leading to improved converter performance and reduced switching losses. The previous cycle's timing information is used to adjust the subsequent cycles.
18. The method of claim 17 , further comprising: adjusting the switching period of the other phases responsive to a transient condition at a load coupled to the multi-phase voltage converter, so that the phases remain aligned during the transient condition.
The method of phase alignment for multi-phase voltage converters includes dynamically adjusting the switching period of the non-reference phases when there's a transient load condition. This ensures the phases stay aligned even during load changes, maintaining zero-current switching and optimal converter efficiency. The controller monitors load fluctuations and adjusts the switching periods dynamically to maintain synchronous rectification despite the transient events, such as step-up or step-down changes in the load.
19. The method of claim 18 , wherein adjusting the switching period of the other phases responsive to a transient condition at the load comprises: increasing the switching period of the other phases by a first predetermined amount responsive to a step-up transient condition at the load so that the phases remain aligned during the step-up transient condition.
When there's a "step-up" transient load condition in the multi-phase voltage converter, the method increases the switching period of the non-reference phases by a pre-determined amount. This adjustment compensates for the increased load, maintaining phase alignment, ensuring zero-current switching, and optimizing the converter's performance during the transient event. The amount of the increase is calculated or determined experimentally beforehand.
20. The method of claim 18 , wherein adjusting the switching period of the other phases responsive to a transient condition at the load comprises: decreasing the switching period of the other phases by a second predetermined amount responsive to a step-down transient condition at the load so that the phases remain aligned during the step-down transient condition.
In the method of phase alignment for multi-phase voltage converters, if a "step-down" transient load condition is detected, the switching period of the non-reference phases are decreased by a pre-determined amount. This adjustment ensures the phases remain aligned during the load decrease, maintaining zero-current switching, reducing switching losses, and optimizing converter performance. The pre-determined value compensates for the reduced load demands.
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May 13, 2016
October 31, 2017
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